<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Flex布局</title>
  <style>
    * {
      padding: 0;
      margin: 0;
      box-sizing: border-box;
    }

    .box {
      display: flex;
      flex-direction: column; /* 修改主轴方向 */
      align-items: center;
      height: 300px;
      border: 1px solid #000;
    }

    .box div {
      /* align-self: stretch; */
      height: 100px;
      width: 200px;
      background-color: pink;
    }
    .box div:nth-child(2){
      align-self: flex-end;
    }
  </style>
</head>

<body>
  <div class="box">
    <div>1</div>
    <div>2</div>
    <div>3</div>
  </div>
</body>

</html>